Previous work with families has suggested that a genetic marker for schizophrenias and for bipolar affective disorders may be found on chromosome 6, associated with the HLA locus. This work is to be extended to more families and to sibships, and to include other markers, particularly Bf and Glo I. A major thrust of the present proposal, however, is to carry out Q, G and C-banding of early metaphase chromosomes of members of nuclear families of probands, the better to characterize the families. This may add to family and personal history, phenomenology, course of illness and response to medication a new factor in diagnosis.